In a spinning mill, raw cotton is first opened by a mixing and blowing apparatus to remove impurities and form a sheet-like lap. Ordinarily, in the final step, a so-called lap machine is used, and the produced lap is wound on a large-diameter bobbin called a spool and to convey it to the succeeding step.
Also in the combing step subsequent to the mixing and blowing step, a sliver lap machine or a ribbon lap machine is used to make a sliver lap or a ribbon lap, which are also wound on a spool and conveyed.
The spool used in these various steps is reciprocatingly moved between the steps for repetitive use, and therefore, in order that it is attached to the lap machine or the like to wind a new lap, it is necessary, as the preparing step, to completely remove a residual lap remaining on the surface of the spool. As apparatus for carrying out such a lap removal work, for example, apparatus comprising a combination of a draft mechanism and an air nozzle has been known (see Japanese Patent Publication No. 54-22528 (1979) official gazette).
According to the aforesaid patent, an unprocessed spool with a residual lap is held on a draft mechanism comprising a pair of parallel rollers and rotated in a direction of unwinding a residual lap and at the same time, an air jet from an air nozzle is jetted in a tangential direction of the spool to effect pick-finding and unwinding of the residual lap.
According to the prior art as just mentioned, the pick finding of the residual lap on the spool exclusively relies upon the air jet. It is therefore necessary for realizing the positive pick finding that the direction of the air jet be accurately registered with the tangential direction of the lap at the extreme end of the residual lap (more accurately, the tangential direction of the surface of the extreme end of the lap of the uppermost layer at the contact portion between said extreme end and the next lap). However, since the amount of the residual lap on the spool is not always constant, it is difficult to always fulfill the aforesaid condition. Thus the prior art unavoidably posing a problem that the pick finding is imperfect, sometimes resulting in a failure of lap removing work.